Ramzi Binalshibh, an admitted al-Qaeda planner of the Sept. 11 attacks, tried four times to join the terrorist hijackers who flew planes into the World Trade Center and the Pentagon in 2001 and has acknowledged his goal of killing as many Americans as possible.

Now the Yemeni man is seeking the help of the U.S. court system to address his complaint that he has been wrongfully imprisoned and treated unfairly by the U.S. government. He filed a legal challenge in federal court in Washington on Oct. 10, asserting his rights to contest his detention and requesting that a court-appointed lawyer represent him free of charge.

In so doing, Binalshibh brought to life the two arguments at the heart of the recent, furious debate over stripping such habeas corpus rights from so-called enemy combatants: the administration's position that alleged terrorists like him do not deserve access to U.S. courts, and his opponents' assertion that the American justice system is a model for the world precisely because it accords such basic rights to all.

One of the most bitterly fought provisions of the legislation President Bush signed Oct. 17 to establish a system of military trials, or "commissions," for accused enemy combatants eliminated those rights for the captives at the U.S. prison in Guantanamo Bay, Cuba. Suspending habeas rights is a step that has been taken only four times previously in U.S. history, and its legality this time will almost certainly be decided by the Supreme Court.

Because of Binalshibh's alleged admission that he was a key player in the Hamburg cell that carried out the attacks, his legal suit may provide the starkest test yet of America's justice system, legal experts said.

"It is how our system treats the worst of the worst, the most reviled of the reviled, that shows how true we are to our principles, " said David H. Remes, who has represented 17 detainees, mostly from Yemen, and coordinated defense arguments to the Supreme Court in the successful Hamdan case.

Binalshibh may never get the hearing he is seeking. His is one of hundreds of cases the government asked the courts to dismiss immediately after Bush signed the new law. For his part, Binalshibh did little more than assert his habeas rights and ask for a lawyer.

Binalshibh is part of a select group of detainees that even defense lawyers acknowledge may be guilty -- 14 suspected terrorists the government deemed "high-value detainees," some of whom have allegedly admitted high-level roles in the al-Qaeda attacks. President Bush cited the 14 men, selected from more than 100 terrorist suspects who had been held for years in secret CIA-run prisons, when he successfully lobbied for the military commission law.

Bush sought Congress's approval after the Supreme Court ruled in Hamdan v. Rumsfeld in June that the administration lacked the authority to establish the military trials on its own. He pressed for the legislation as the government transferred the 14 men to a unit of the military prison in Guantanamo Bay and singled out Binalshibh -- along with Sept. 11 mastermind Khalid Sheik Mohammed.

Binalshibh's family's decision to seek help in a U.S. court also highlights a growing tension within the defense bar about the ethical and practical dilemmas of representing detainees who likely played a role in slaughtering thousands of Americans.

Binalshibh's brother filed a petition on his behalf and asked the federal court to appoint a public defender to represent him. The Center for Constitutional Rights, a civil liberties group that sued last year to represent the remaining detainees in Guantanamo Bay who lack representation, is not currently representing him. A group official said he could not comment on the reason because of potential attorney-client privilege.

Tina Foster, a civil liberties lawyer who previously helped coordinate the work of dozens of law firms representing hundreds of Guantanamo detainees, said it would be a "challenge" to find a pro bono lawyer for Binalshibh because he has been virtually convicted in media reports as a Sept. 11 plotter. Remes said there is an "understandable reluctance" among large commercial law firms to champion Binalshibh's cause.

"You wouldn't be rushing to file a habeas claim for Ramzi Binalshibh," Foster said. "Most of the folks down there are "no-value" detainees -- they shouldn't even be there -- and those are the ones you'd want to push in the court."

Binalshibh was captured by the United States in Pakistan in 2002 and taken to secret detention facilities. According to the Sept. 11 commission, he told interrogators that he was supposed to pilot another hijacked airliner on the day of the attacks but was repeatedly refused a visa to enter the United States.

His transformation to a terrorist began in 1997 when he became friends with future hijackers Mohamed Atta, Marwan al-Shehhi and Ziad Jarrah while living in Germany on a student visa. He later pledged allegiance to Osama bin Laden while training with his friends in Afghanistan in 1999.

Instead of participating in the attack, Binalshibh relayed messages between the hijackers and Mohammed, met with Atta for briefings on attack planning and allegedly helped transfer money to the hijackers.